I'm a lowly physics I student, but isn't that the whole theory behind 0K? At that temperature molecules cease to move?

It is if you consider only classical thermodynamics. However, once you get to temperature range that low, quantum effects will kick in and you simply can't extrapolate all that you've known at higher temperatures down to such low temperatures. We have already seen how such things break down when certain material instead becomes a superfluid.

It is if you consider only classical thermodynamics. However, once you get to temperature range that low, quantum effects will kick in and you simply can't extrapolate all that you've known at higher temperatures down to such low temperatures. We have already seen how such things break down when certain material instead becomes a superfluid.

Zz.

So, in other words we really don't know what will happen at absolute zero 100% of the time?

So, in other words we really don't know what will happen at absolute zero 100% of the time?

It depends on the substance.

Note that for a quantum harmonic oscillator, the lowest energy state that it can occupy is [itex]\hbar\omega/2[/itex]. So if you have molecules or solids that can be described by such harmonic oscillators, we already know that they do not stop moving, since there are no lower state than that.

Furthermore, in noble gasses, we have also seen a deviation in the specific heat measurement as you approach very low temperatures. The deBoer effect observed in such measurements can clearly be attributed to such zero-point energy, where by such quantum effects will start kicking in.

In order for a substance to be at absolute zero, it's atoms but be absolutely still. However, if this were the case, we could know the position and momentum (0) of a particle exactly, which goes against quantum mechanical principles.